Abstract:

Gas-liquid two-phase flow occurs in safety valve calculations in the process industry. In order to size the safety valves reliably, the pressure drop calculations of the two-phase flow needs to be accurate. Two-phase flow is affected by many variables such as the viscosity. The aim of this thesis is to implement reliable and accurate calculation methods for viscosity and pressure drop for two-phase flows in a dynamic process simulator, ProsDS. Furthermore, the effect of viscosity on two-phase flow is studied.

The literature part of this thesis consists of two main chapters. In the first chapter, the viscosity methods for gas and liquid phases are reviewed. In addition, the viscosity methods for petroleum fractions and crude oils are introduced. The second chapter focuses on the two-phase flow. Different variables related to two-phase calculations, flow patterns and pressure drop calculations methods are introduced. The effect of the viscosity on the two-phase flow is studied in the end of the second chapter.

The applied part is also divided into two sections. In the first part, the most accurate and practical viscosity methods of FLOWBAT simulator were integrated into ProsDS. The methods were verified using experimental values presented in the literature. In the second part, several two-phase pressure drop methods were compared to the experimental values from the literature containing gas-liquid flows with various viscosities. Pressure drop methods of Lockhart-Martinelli, Müller-Steinhagen-Heck and Bandel gave the most accurate results and they were implemented into ProsDS. The methods were tested in a safety valve inlet piping case. The results of the simulated case differed significantly from each other. The inconsistency of the results indicates that it is difficult to predict two-phase pressure drops reliably.Kaasua ja nestettä sisältävää kaksifaasivirtausta esiintyy prosessiteollisuuden varoventtiilitapauksissa. Varoventtiilien mitoituksen luotettavuuden parantamiseksi kaksifaasivirtauslaskentaa tulisi tarkentaa. Kaksifaasivirtaus riippuu monista muuttujista kuten esimerkiksi viskositeetistä. Tämän diplomityön tarkoituksena on implementoida tarkat ja luotettavat menetelmät viskositeetin ja kaksifaasivirtauksen painehäviön laskemiseen dynaamisessa prosessisimulaattorissa, ProsDS:ssa. Lisäksi työssä tutkitaan viskositeetin vaikutusta kaksifaasivirtaukseen.